The present invention relates to a stack handling operation technology, and more particularly to technology for providing a faster stack handling operation sequence with as little cost as possible when restacking a plurality of stackable items from an initial state to a target state.
In industry, restacking may be necessary for a plurality of stackable items from an initial state to a target state in various situations. For example, in a steel plant with two consecutive processes including a steel manufacturing process and a hot rolling process, manufactured products and semi-manufactured products that weight 10 tons or more are stacked as interim inventory. These manufactured products and semi-manufactured products are fundamentally all unique, and because the output sequence of items from the steel manufacturing process and the input sequence for the rolling process are generally different, the stacked items are required to be sorted by a crane into the sequence of treatment by the hot rolling process. Reducing the cost of sorting (normally defined as the number of crane operations) is extremely important, leading not only to cost reduction, but also leading to improvement in throughput before and after processing. Currently, creation of the crane handling operation sequence is left to the intuition and experience of the crane operator (human), creating a large potential loss.
Furthermore, generally, automatic creation of a production schedule by a computer is possible for the hot rolling process and the like. When the production schedule is created by a computer, a huge number of production schedule candidates are created. In this case, the cost of sorting before the hot rolling process is preferably considered for each candidate. In order to implement this, an approximate solution (a specific handling operation sequence is not required, but a rough calculation of only the cost is sufficient) must be calculated at high speed.
Background references include Japanese Unexamined Patent Application 2011-105483 and Japanese Unexamined Patent Application H07-290125.